Screening of Spices for Bioactive Compounds and Their Effect on In Vitro Fermentation Pattern and Methanogenesis from Total Mixed Ration

In vitro gas production studies were conducted to assess the impact of six spices (viz. turmeric, clove, oregano, ajwain, cinnamon and ginger) on the rumen fermentation pattern and methane production. Spices were supplemented at 0, 1, 2 or 3% on DM basis to the total mixed ration (TMR) containing concentrate mixture and oat fodder in a 40:60 ratio on DM basis. The data were analyzed by one-way ANOVA and 4 x 6 factorial design. Screening of spices for bio-active compounds revealed the highest concentration of total phenolics, flavonoids and Vitamin C activity in clove, saponins in turmeric, essential oils in oregano and 2, 2-diphenyl-1-picrylhydrazyl (DPPH) activity in ajwain, respectively. Irrespective of the level of supplementation, the diet supplemented with cinnamon had the highest (P<0.01) net gas production (NGP) and metabolizable energy (ME). The diet supplemented with turmeric had the highest (P<0.01) digestibility of true OM and NDF, partitioning factor (PF), total VFAs and propionate concentration, acetate to propionate ratio, highest rumen fermentation efficiency and lowest methane production. Irrespective of the nature of spices, as compared to the unsupplemented TMR, the TVFAs and acetate production, fermentation efficiency and VFAs utilization index expressed by Non-Glucogenic/ Glucogenic ratio (NGGR) were improved (P<0.01) at 1% level of supplementation, but beyond this level the differences were non-significant. It was concluded that the digestibility of nutrients, VFA production, rumen fermentation efficiency, and methane mitigation potential can be improved by supplementing the diet with turmeric at 1% on a DM basis.